The entire disclosure of Japanese Patent Application No. 2000-400039 filed on Dec. 28, 2000, including specification, claims, drawing, and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a method and apparatus for producing methanol making use of biomass as raw material.
2. Background Art
Production of methanol by use of biomass such as plants as a raw material is carried out on the basis of the following reactions.
CH2O+xc2xdO2xe2x86x92CO+H2Oxe2x80x83xe2x80x83(1) 
CO+H2O←xe2x86x92H2+CO2xe2x80x83xe2x80x83(2) 
CO+2H2xe2x86x92CH3OHxe2x80x83xe2x80x83(3) 
Briefly, carbon monoxide (CO) and hydrogen gas (H2) which have been produced through partial combustion or steam-gasification of biomass (CH2O) are caused to react, to thereby produce methanol (CH3OH).
As used herein, the term xe2x80x9cpartial combustionxe2x80x9d refers to a type of combustion in which a portion of biomass is subjected to combustion including complete and incomplete combustion.
As is clear from scheme (2), the aforementioned reactions include a shift reaction; i.e., when an attempt is made to increase the amount of carbon monoxide to be produced, the amount of hydrogen to be produced decreases, and when an attempt is made to increase the amount of hydrogen to be produced, the amount of carbon monoxide to be produced decreases. Generally, the reaction is shifted to the left side, where the amount of carbon monoxide to be produced increases. Therefore, the amount of hydrogen for producing methanol becomes insufficient, and the produced carbon monoxide cannot be used effectively.
One possible measure to solve this problem is to supply water (steam) to the reaction system, to thereby shift the reaction to the right side of the aforementioned scheme (2) so as to generate hydrogen of a required and sufficient amount. However, when the amount of supplied steam increases, the temperature in the reaction system is lowered, to thereby retard rate of reaction and problematically reduce efficiency of methanol production.
In view of the foregoing, the present inventors carried out extensive studies so as to solve the problems, and have found that methanol can be produced effectively by supplying hydrogen gas to a gas produced by gasifying biomass in a conventional method for producing methanol making use of biomass material. Thus, an object of the present invention is to provide a method for producing methanol making use of biomass material, which method is capable of making effective use of produced carbon monoxide without deteriorating efficiency of methanol production. Another object of the invention is to provide an apparatus for producing methanol.
Accordingly, in a first aspect of the present invention, there is provided a method for producing methanol making use of biomass material comprising gasifying biomass to produce a gas; and supplying hydrogen gas to the produced gas, to thereby produce methanol.
Preferably, hydrogen gas is supplied to the produced gas such that the amount of hydrogen gas is adjusted to at least twice the amount of carbon monoxide contained in the produced gas.
Preferably, hydrogen gas generated through electrolysis of water is supplied to the produced gas.
Preferably, oxygen gas generated through electrolysis of water is employed as a gasification agent for the biomass.
Preferably, hydrogen gas and oxygen gas generated through electrolysis of water are temporarily reserved separately before use.
Preferably, water is electrolyzed by electric power obtained by use of natural energy (i.e., energy obtained from natural resources).
Preferably, the electric power obtained by use of natural energy is temporarily stored before use.
Preferably, the natural energy is at least one type of energy selected from among sunlight energy, wind energy, tidal energy, hydraulic energy, and solar thermal energy.
In a second aspect of the present invention, there is provided an apparatus for producing methanol making use of biomass material comprising biomass gasification means for producing a gas through partial combustion or steam-gasification of biomass; methanol synthesis means for producing methanol from the thus-produced gas; and hydrogen gas supplying means for supplying hydrogen gas to the produced gas.
Preferably, the hydrogen gas supplying means supplies hydrogen gas to the produced gas such that the amount of hydrogen gas is adjusted to at least twice the amount of carbon monoxide contained in the produced gas.
Preferably, the hydrogen gas supplying means includes water electrolysis means for electrolyzing water.
Preferably, oxygen gas generated through electrolysis of water by means of the water electrolysis means is supplied, as a gasification agent, to the biomass gasification means.
Preferably, the above apparatus for producing methanol further comprises oxygen gas reserving means for temporarily reserving oxygen gas generated through electrolysis of water by means of the water electrolysis means, and the hydrogen gas supplying means includes hydrogen gas reserving means for temporarily reserving hydrogen gas generated through electrolysis of water by means of the water electrolysis means.
Preferably, the above apparatus for producing methanol further comprises natural-energy-based power-generation means for operating the water electrolysis means through power generation making use of natural energy.
Preferably, the natural-energy-based power-generation means includes electric power storage means for temporarily storing electric power.
Preferably, the natural-energy-based power-generation means generates electric power by use of at least one type of energy selected from among sunlight energy, wind energy, tidal energy, hydraulic energy, and solar thermal energy.